Hatching experiment failure?

I have a little broody Phoenix hen (she's bantam, but maybe they all are) So, since her eggs are not fertile, I gave her a couple duck eggs. Two, that is all that fits there. Things seem to be going great until today. No, I have not been able to candle them, but other than that seems great. Today she had to relieve herself. She's had to go a couple other times but has gone away from the eggs. Today, it was all over the eggs. So she moved over one hay pile and went to work brooding again, leaving the filthy eggs where they were. Well, when I discovered it the temp was just beginning to drop. It had been 70 and now it was 50. I cleaned the major gunk from the eggs and handed them to the hen who promptly stored them away. I attempted to candle them (13 days) and decided that I had no clue.

So, do I call the whole project a loss or let her sit a bit longer. I think that I could set some more under her, but I'm not sure how long I should expect her to brood or if I should do it back-to-back if I do get a hatch?

@spiritbrook I am with Amiga let her finish I've had hens go off the eggs long enough for them to cool down and when I have found her I put her back on the eggs and they have hatched so it is defiently worth trying.